Conventionally, a wireless camera is used to photograph a relaying scene for televising news programs, sports programs, various event programs, etc. This wireless camera generates a video or voice signal and transmits the signal to a base station such as a relay mobile by means of the ground wave radio communication. Compared to a cable-connected camera, the wireless camera saves labor of installing or removing cables and increases flexibility of camera angles and photographing positions. This improves mobility of the camera at the scene.
Further, in recent years, the wireless camera transmission system is increasingly using a digital modulation system which digitizes video or voice signals.
It is important for a relay system using the digitized wireless camera to improve transmission quality between the base station such as a relay mobile and the transmitting camera so as to ensure stable reception even under a so-called fading environment. It is desired to widen the movable range of the camera for ensuring the mobility essential to the wireless camera. For example, it is desired to receive a transmission signal from the camera by using a plurality of antennas arranged at positions differing from each other for a wide range of reception.
The so-called diversity reception system is known as a radio transmission technology capable of providing high transmission quality. This system receives a transmission wave by means of a plurality of antennas and selects or synthesizes received signals in the RF/IF region according to the levels. However, the diversity reception requires selection and synthesis in the RF/IF region, causing a restriction of arranging a plurality of antennas physically close to each other. Accordingly, the use of the diversity reception technology has been difficult when a plurality of receivers are arranged at different positions for ensuring the wireless camera's mobility.